The benefits of electrical stimulation to increase the tenderness of meat product are well known in the art of meat processing. In fact, the use of electrical stimulation to improve the tenderness of meat has been used since at least as early as 1749 by Benjamin Franklin, who first found that turkey meat was tenderer if the bird was killed by an electric shock rather than by other methods. It is believed that electrical stimulation at least accelerates the process of rigor mortis and prevents “cold shortening” as the carcass is immediately chilled to prevent bacterial contamination. Cold shortening is caused by the release of stored calcium ions from the sarcoplasmic reticulum of muscle fibers in response to cooling of carcass. The calcium ions trigger powerful muscle contractions aided by ATP molecules. To prevent cold shortening, the muscles of the carcass may be electrically stimulated, thereby causing them to contract and relax, which depletes the ATP reserve from the carcass and prevents cold shortening.
One problem associated with electrical stimulation is that the application of electric current to the carcass is known to generate heat in the muscles of the carcass and increase the internal muscle temperature of the carcass. As explained by U.S. Pat. Nos. 6,290,592 and 6,364,759, the entireties of which are incorporated by reference herein, if the meat of the carcass is not cooled to at least a minimum level, i.e. below about 65° F., prior to the completion of rigor mortis, a condition called pale soft exudative (PSE) may result that causes the slaughtered meat to be pale in color, soft and watery. Moreover, if the meat temperature is too high when the muscle enters rigor mortis, the meat will have a tendency to lose moisture content or purge its natural juices, be pale in color, and be softer than normal when the meat cools to its desired level. Excess purge from PSE meat is a significant problem in the meat processing industry.
U.S. Pat. Nos. 6,290,592 and 6,364,759 each point out that particular portions of an animal carcass are particularly susceptible to purge problems. The beef industry generally categorizes the animal carcass, whether split or whole, into at least three sections: the midsection, chuck, and round. The midsection generally includes the thinner muscles of the rib and loin that are generally characterized as extending from about between the fifth and sixth thoracic vertebrae and about between the fourth and fifth sacral vertebrae. The anterior portion of the animal carcass includes the shoulder muscles that the beef industry refers to as the chuck. The posterior end of the animal carcass includes the hind limb muscles that the beef industry generally refers to as the round. Generally, the muscles of the chuck and round are thicker and denser than the thinner muscles of the rib and loin. Accordingly, the chuck and round muscles, if electrically stimulated, generally take more time to cool and are more susceptible to excessive purge.
The solution to minimize purge problems in the thicker meat sections offered in U.S. Pat. Nos. 6,290,592 and 6,364,759 is to isolate the muscles of the anterior end section (chuck) and posterior end section (round) to provide electrically stimulated muscles in the midsection and non-electrically stimulated muscles in the anterior and posterior end sections. In one embodiment, as shown in Prior Art FIG. 1, U.S. Pat. Nos. 6,290,592 and 6,364,759 disclose an electrical stimulation apparatus 5 having three distinct sharpened aluminum stakes, each of which are inserted into the muscles of the carcass 1. One “hot” stake 7 is inserted into the muscles of the midsection 9 of the animal and two ground stakes 11, 13 are inserted into the muscles of the posterior end section 15 in the vicinity of the fourth or fifth sacral vertebrae (separation point of the carcass loin 17 and round 19 section) and into the muscles of the anterior end section 21 in the vicinity of the fifth and sixth thoracic vertebrae (separation point between the rib 23 and chuck 27 sections) respectively. In this way, the muscles of the chuck and round of the animal are isolated from receiving electrical stimulation, thus precluding purge problems in the isolated chuck and round sections.
In another embodiment, as shown in Prior Art FIG. 2, U.S. Pat. Nos. 6,290,592 and 6,364,759 disclose an apparatus having upper grounds 424, 430 that contact the animal carcass in the posterior end section of the carcass at a location corresponding to between about the eleventh thoracic vertebrae and about the second lumbar vertebrae. The apparatus further includes lower grounds 426, 432 that contact the animal carcass in the anterior end section of the carcass at a location corresponding to about the fifth and sixth thoracic vertebrae. A plurality of electrical stimulation probes 450 are provided that extend into the path of travel of the animal carcass, preferably at an angle of about 50 to 130 degrees, to contact the animal carcass in the midsection of the animal. In this way, the muscles of the midsection are electrically stimulated while the muscles of the chuck and round of the animal are isolated from receiving electrical stimulation, thereby precluding purge problems in the isolated chuck and round sections.
While U.S. Pat. Nos. 6,290,592 and 6,364,759 disclose methods and apparatuses that address purge problems in the chuck and round sections by preventing the muscles of the chuck and round from being electrically stimulated, the methods and apparatuses of U.S. Pat. Nos. 6,290,592 and 6,364,759 actually deprive the chuck and round, which still contain valuable meat sections for commercial sale, of the well-known benefits of electrical stimulation, including tenderizing of the meat. Thus, there is a need for a method and apparatus for electrically stimulating an animal carcass, including thick meat sections thereof, without the undesired purge problems associated with known methods of electrical stimulation.
These and other advantages will be apparent from the disclosure of the invention(s) contained herein. The above-described embodiments and configurations are neither complete nor exhaustive. As will be appreciated, other embodiments of the invention are possible using, alone or in combination, one or more of the features set forth above or described in detail below.